Virtualization technologies, such as server clustering and virtual-machine hypervisor may rely on the extension of virtual local area networks (VLANs) across geographically dispersed sites, such as data centers. One or more of these sites may utilize spanning tree protocol (STP) to implement a loop free topology within the site. However, STP does not perform well in large-scale networks and is generally not used to interconnect multiple sites.
Some sites may utilize flexlink (e.g., CISCO FlexLink) connectivity on one or more devices in place of STP. A flexlink may include a pair of layer 2 (referring to the Open Systems Interconnection (OSI) model) interfaces on a device. Such a configuration may provide layer 2 redundancy for a device without requiring STP on the device to ensure loop-free topology. Redundancy may be achieved by configuring one interface as a primary (active) interface and one interface as a backup (standby) interface where only the primary interface is active and forwards traffic. Flexlinks are typically implemented by devices at the access layer of a site.